November 19, 2012

Maine towns monitoring their road salt diet

Road salt, the region's favored ice-melting agent, is inexpensive, but can take a toll on the environment.

By Matt Hongoltz-Hetling
Staff Writer

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Waterville Public Works Director Mark Turner said the department uses a ratio of 17 parts sand to one part salt on city roads. "We've found over the years that's the best mixture, " he said.

Photo by Jeff Pouland

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Farmington Director of Public Works Denis Castonguay shows a small computer inside one of the town plow trucks. The equipment can be programed for the most efficient use of salt on winter roads, in terms of both economic and environmental impact.

Staff photo by David Leaming

Area towns were asked how much road salt they used last year and how many lane miles they used it on.

Farmington: 784 tons on 240 lane miles = 3.26 tons per lane mile

Waterville: 1,500 tons on 280 lane miles = 5.35 tons per lane mile*

Winslow: 1,000 tons on 172 lane miles = 5.8 tons per lane mile

Skowhegan: 1,150 tons on 192 lane miles = 5.99 tons per lane mile

Oakland: estimated 450 tons on 68 lane miles = 6.62 tons per lane mile

Augusta: 2,800 tons on 350 lane miles = 8 tons per lane mile **

Fairfield: 1,198 tons on 120 lane miles = 9.98 tons per lane mile

* Waterville Public Works Director Mark Turner said that the city also treats a significant amount of non-road pavement with its 1,500 tons, which he estimates at about 10 percent of the total lane miles. An adjusted figure based on that estimate is 4.87 tons per lane mile

** Augusta said there was a lot of ice last year, necessitating additional salt. Officials said the previous year, 2,200 tons were used, which was more typical. That year, the figure would have been 6.28 tons/lane mile.

Unlike in many towns, Castonguay has a laser-based temperature sensor in his truck that he uses to read the road temperature, an important data point that can make salting more efficient.

Still, he said, he sees room for improvement.

"We're about 10 years behind the technology that's out there," he said.

Fairfield Public Works Director Bruce Williams said he isn't sure why his town uses more salt than others in the area. Town Manager Josh Reny pointed out that the town has no salt-priority roads, which are treated exclusively with salt, instead of a sand and salt mixture.

It seems obvious that roads requiring only salt would get the most, but Castonguay said the opposite is true. During a storm, he said a salt-priority road that has been pretreated with a relatively small amount of salt will melt snow as it lands. When plows revisit a stretch of road multiple times during a storm while spreading a sand and salt mix, it creates layers of icy grit on the road that then has to be melted with more salt at the end of the storm.

The Department of Environmental Protection is hosting a workshop in Augusta Nov. 27 and Portland Nov. 20 to help plow operators manage salt more effectively. Spokeswoman Samantha Depoy-Warren asked plow operators and others who are responsible for snow removal to call 215-9110 to learn more and register for the free sessions.

Changing times

Brian Burne, highway maintenance engineer for the Maine Department of Transportation, said strategy to reduce salt continues to evolve.

"It's a big change from the days when we would drive around and throw sand out the back," he said.

The state's plow trucks, and most trucks in most towns, are equipped with computer control systems that spread salt optimally for factors like truck speed, air temperature and storm condition.

In Farmington, Castonguay said, the systems, which cost a few thousand dollars apiece, pay for themselves in a single winter by reducing salt cost. Data from infrared temperature sensors mounted on the side of plow truck mirrors is fed into the computer system for more efficient plowing.

Some alternative substances are inexpensive but unproven or are associated with different environmental concerns. Others work only during a fairly narrow range of storm conditions. And others are consistently effective but cost too much.

According to Burne, one alternative, calcium magnesium acetate, is about 15 times more expensive than road salt.

"If we switched entirely over to that, it would eat up our entire budget so we couldn't pay for people or equipment," he said.

One product that has gotten a lot of attention recently is Ice B'Gone, a beet sugar based additive that gums up rock crystals, preventing them from bouncing off the road and into a ditch without melting any ice. The liquid, which has been endorsed by the federal Environmental Protection Agency, also helps the salt to be effective at lower temperatures.

Many public works directors are taking a wait-and-see approach to the relatively new product but it is in use by the state transportation department and in Skowhegan, where Road Commissioner Greg Dore said it has helped to reduce the amount of salt used by about half.

Burne said even more advanced equipment remains beyond the reach of the state. One example is flexible rubber-treated carbide blades that will mold to the contours of the pavement, which leave less snow behind to be melted. Another is a GPS system that automatically adjusts the amount of salt being spread using real-time information such as the vehicle location, traffic flow and weather systems.

All of the public works directors agreed that there's another obstacle to reducing salt: changing public expectations.

They said it wasn't that long ago that roads would go unplowed for days after a storm and people traveled at their own peril.

The directors said more people now expect to be able to drive fast during and after a snowstorm, which requires more resources, including more salt.

Matt Hongoltz-Hetling -- 861-9287


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